The cyborg commando is pretty powerful, and he can probably kill all of the
GDI forces on the map by himself. So just about any path you take will
allow you to finish the mission successfully. This is just one way.

Follow the mutant guide east. He's under computer control, and he'll
remain that way for the remainder of the mission. He'll probably also
get killed because he runs right into a GDI patrol.

Mop up the patrol with your units, and then have an engineer fix the
bridge. Be careful crossing the bridge because there are a titan and
hover tank in the area, and the bridge is fragile. One hit will break
it and send whatever units you have on it down the river.

After killing the titan and hover tank, move north along the coast.
You'll come to a ramp leading north. Sending a unit up the ramp will
trigger a meteor shower, so use one of your engineers.

Beyond the ramp to the north is the base with the bio-toxin trucks. The
buildings are damaged, but you can use an engineer to fix one, or sell
the gate and use the resulting credits to repair the buildings normally.
There is a hospital in the base, and the cyborg commander can use it to
be restored to full health.

The checkpoint area where you need to send the trucks will also be
revealed. It is east of the base, beyond a small GDI outpost. The
outpost is guarded by a vulcan cannon and a titan, plus a few infantry
units. The cyborg commando has better range than the cannon, so
dispatching that should be no problem, and the commando and your
remaining units should be able to kill the titan quickly. Now just
send the trucks to the checkpoint to finish the mission.